1. Field of the Invention
The present invention generally relates to Quality of Service (QoS) in a Differentiated Service (DiffServ) network. More particularly, the present invention relates to a method and apparatus for guaranteeing QoS in a residential Ethernet system.
2. Description of the Related Art
Ethernet is one of the most widely installed technologies for data transmission between different terminals. Owing to its universality and simple structure, Ethernet extends its applications to a Local Area Network (LAN) and a Wide Area Network (WAN). Although it is known that Ethernet is not suitable for transmission of delay-sensitive multimedia data, studies have been actively conducted on a technology for transmitting multimedia data including audio and video, while ensuring compatibility with legacy Ethernet networks. The technology is called Audio/Video (AV) bridging or residential bridging, now under standardization in Institute of Electrical and Electronics Engineers (IEEE) 802.1 protocol.
Meanwhile, two Internet solutions for end-to-end QoS guarantee are attracting interest as a substitute for the existing best-effort service. One is rather simple, called Integrated Service (IntServ) which relies on a receiver-initiated signaling protocol, resource ReSerVation Protocol (RSVP). IntServ provides QoS to end hosts by reserving end-to-end resources using the RSVP, when the end hosts signal their QoS needs.
IntServ provides three service classes, best-effort service, guaranteed service, and controlled load service. For packets of the service classes, path setup and resource reservation are essential before data transmission. However, performing the resource reservation process in all routers existing on a path brings about a load large enough to significantly affect the whole system.
The other Internet QoS solution is DiffServ. Instead of reserving resources on a per-flow basis, an edge node (e.g. router) classifies data packets according to user-requested QoS levels and a core node of a network forwards the traffic differentially, to thereby provide differentiated services to users. Thus, DiffServ obviates the need for a resource reservation protocol and resource reservation and offers the benefits of small network load and provisioning of differentiated services.
Differentiated Service Code Point (DSCP) representing precedence is set in Type of Service (TOS) of the header of an Internet Protocol (IP) datagram. For DSCP, four values are defined: Default Per-Hop-Behavior (PHB), Assured Forwarding (AF) PHB, and Expedited Forwarding (EF) PHB. A core router processes a high-precedence packet first of all according to a DSCP setting. In this way, differentiated services are provided.
The edge router has five components, classifier, meter, marker, shaper, and dropper to implement differentiated traffic control. The classifier classifies received traffic based on various criterions. The meter measures the classified traffic flow and compares the measurement with a predetermined traffic profile so that the marker can mark the traffic flow appropriately. Marked packets are controlled in accordance with a predetermined bandwidth characteristic for traffic by the shaper that controls a bandwidth by delaying and the dropper that controls a bandwidth by dropping.
FIG. 1 illustrates a typical DiffServ network for QoS guarantee. Referring to FIG. 1, an edge router sets a DSCP in an IP packet and sends the IP packet to a core router 12. The core router 12 performs a PHB according to the DSCP value. While the core router 12 may have a relatively simple structure as it only has to forward the IP packet between hops, the edge router 11 has a complex configuration due to classification and conditioning.
Both IntServ and DiffServ present QoS guarantee solutions over IP version 4 (IPv4) and IP version 6 (IPv6) networks. Yet, they are confined to router-based Layer 3 (L3) networks and not effective in ensuring QoS for transmission of time-sensitive data such as Voice over Internet Protocol (VoIP) in a Layer 2 (L2)-based edge network that interfaces with L3 or higher networks. Especially in Wireless Broadband (WiBro), there is no specified method for ensuring QoS in an L2 network between a Radio Access Station (RAS) and an Access Control Router (ACR). While RSVP-based IntServ or DiffServ exists in an L3 or higher network where the ACR communicates with an external network, no QoS guarantee for L2 may cause a severe bottleneck phenomenon. As a result, jitter or latency, or even packet loss may happen.
For background details of the L2-based WiBro network, see Korea Patent Application No. 2006-60848 entitled “Bridge-Type Portable Internet System and Signal Processing Method Thereof” and filed on Jun. 30, 2006 by the present applicant (U.S. Ser. No. 11/644,575 filed on Dec. 22, 2006) or Korea Patent Application No. 2006-68828 entitled “Bridge-based Base Station backbone System and Signal Processing Method Thereof” and filed on Jul. 24, 2006 (U.S. Ser. No. 11/880,659, filed on Jul. 24, 2007) by the present applicant.